After much anticipation, and against the wishes of the international community, North Korea finally pushed the button on its third underground nuclear test, this time using more sophisticated technology than its previous attempts.

While it marks another milestone in the short, but increasingly eventful, reign of young leader Kim Jong Un, it also threatens to undermine an already fragile security situation in the region.

How worried should we be about North Korea's nuclear test?

It's worrying but does this mean they can drop a nuclear weapon on Los Angeles? Absolutely not. The notion that they are going to target the U.S. is way off the mark.

Any time the North Koreans stage a test, it significantly improves their nuclear capabilities. This comes after they staged a rocket launch that was successful, a long range rocket which appears to have put a satellite into orbit. What they need to achieve to have the weapon they want is the capability to miniaturize a warhead and put it on a rocket. This test isn't going to do that in and of itself, but it is a significant step forward.

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China's role in Korean crisis

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China's role in Korean crisis 06:59

The U.N. Security Council will meet. South Korea is the chair this month so they get to call the agenda. There will be discussion about a much tougher sanctions resolution. The $64,000 question is whether the Chinese will in the end agree to anything significant enough for it to really affect North Korea.

I think it's certain, whatever the U.N. does, the U.S. will move on its own to ratchet up sanctions. I also think the Americans will beef up their military presence in the region. It will mean stronger anti-missile defenses going to South Korea and possibly Japan

Why is China's reaction so important?

The Chinese don't like the idea of international sanctions and coercing other countries. They still have a strategic interest in maintaining a viable separate North Korea as a buffer against a pro-U.S. South Korea and that has only become more important as tensions between the U.S. and China have increased.

On the other hand, a nuclear North Korea that is behaving in an adventuristic way risks very bad outcomes from the Chinese point of view. What China least wants is a more active, antagonistic, robust U.S. military presence in North East Asia in conjunction with the strengthening of military capabilities of allies who are not China's friends.

Chinese companies are more involved in North Korea than they were half a dozen years ago, so the Chinese stand to lose on that front if the U.S. tightens sanctions.

Who really calls the shots in North Korea?

(North Korean leader) Kim Jong Un has people around him but he's driving the show. There's no evidence to suggest that he's not in charge. All the personnel changes he made he was able to make without enough pushback for it to matter. He's got military people around him, and his uncle. I don't see any evidence to see that he's not ultimately in charge.

How significant is the timing of the test?

It's the birthday of Kim Jong Il (Kim Jong Un's late father) on (Saturday). Assuming this (test) is not a total dud, this will be ... great propaganda and they will play it to the hilt. North Koreans are extremely nationalistic. They may be hungry, they may be miserable but by God they've got a bomb and they can stand up to the rest of the world and that really, really matters in North Korea.

You also have a power transitions in Seoul, Tokyo (and the U.S.). How can Barack Obama not devote more attention to North Korea in his State of the Union address? Everyone is reacting to them and that's how they (North Koreans) like it.

What don't we know?

We don't know yet whether this was a test of a plutonium device or a uranium device. The previous two tests were plutonium. We know they have a uranium enrichment capability. We know that a uranium bomb, once they master it, is easier to make and they have deposits of uranium in North Korea so they can keep digging it up.

If they have successfully detonated a uranium bomb and they have moved forward in the process of developing the technical capabilities to miniaturize it and put it on a war head, then in purely military terms it's worrying

The test also raises interesting questions on the proliferation front. The more successful they are with this program, the scarier the consequences should they choose, for example, to provide Iran with test data or fissile material or other information.